In recent years, soy sauce has been used as a seasoning in larger variety of processed foods. It seems that the traditional regular brewed soy sauce cannot satisfy some of the diverse consumer demands. There is particularly a strong demand for light-colored and reduced-smelling seasoning that does not harm the color and flavor of the processed foods but that can still add the savory taste of soy sauce to the processed foods. Furthermore, although consumer demands are various, their basic request is that the seasoning should be produced by brewing the raw material with microorganisms, not produced chemically or enzymatically like hydrolyzed vegetable protein (HVP).
Japanese examined patent publication (koukoku) H7-20426 (1995-20426) discloses a method of producing soy sauce in which warmed salt water is added to a mixture of defatted soybean and koji mold. Then, the moromi is maintained at 37-43° C. and its salt concentration is adjusted to be 8-12%. Furthermore, the fermentation is maintained for 5-20 days after adding the yeast. Thereby, soy sauce that has lighter color and milder smell is obtained. However, this method needs to maintain the moromi at 37-43° C. Thus, the energy cost for brewing is higher than the regular soy sauce brewing. This results in high manufacturing costs. In addition, this method brews the moromi in salt water which has low salt concentration. Thus, there is a risk that putrefactive bacteria grow. To suppress the growth of putrefactive bacteria, the moromi is maintained at high temperature. However, this also suppresses the fermentation by lactic acid bacteria. Thus, soy sauce obtained by this method has low content of lactic acid, which contributes to the profound taste of soy sauce. Also, the low lactic acid concentration is considered to lower the mold prevention ability of the soy sauce.
In Japanese Patent 4716369, about 150% of water is added to the moromi. Then, the moromi is cultured after adding Zygosaccharomyces yeast. However, even in this method, because the yeast growth is facilitated by the dilution of moromi, the color of the soy sauce becomes dark, and the smell caused by the yeast also increases.
Japanese Patent Application Publication H10-66539 (1998-66539) and Japanese Patent Application Publication H10-99043 (1998-99043) disclose a method of producing a seasoning by hydrolyzing a mixture of fermented koji protein and yeast at 2-25° C., at pH 4.5-10 and for 6 hours-28 days. These documents suggest that brewing moromi is unnecessary because cohydrolysis occurs, resulting in a lower concentration of reducing sugars. However, this method is concerned to result in the low amount of lactic acid, which is generated by lactic acid fermentation, as well as other flavorful constituents generated by the maturation of fermentation. Therefore, the flavor of the seasoning obtained by these methods is considered to be different from the flavor of soy sauce. Furthermore, the acid hydrolysis solution obtained by acid-hydrolyzing protein sources such as soybean or wheat gluten lacks aromatic components and constituents that are generated by fermentation. In addition, levulinic acid and formic acid are generated during the acid hydrolysis. Therefore, the composition and taste of this seasoning is very different from those of brewed soy sauce.
International publication WO2011/030779 reports the method of producing a seasoning powder. In this method, protein material is hydrolyzed with cultured liquid koji. Then, the hydrolysate is spray-dried without removing the solid components generated by hydrolysis. However, this seasoning is a hydrolyzed vegetable protein (HVP) and totally different from soy sauce.